Anatomic and neurochemical analysis of the palpal olfactory system in the red flour beetle Tribolium castaneum, HERBST

Björn Trebels; Stefan Dippel; Janet Anders; Clara Ernst; Brigitte Goetz; Tim Keyser; Karl Heinz Rexer; Ernst A Wimmer; Joachim Schachtner

doi:10.3389/fncel.2023.1097462

Anatomic and neurochemical analysis of the palpal olfactory system in the red flour beetle Tribolium castaneum, HERBST

Front Cell Neurosci. 2023 Feb 23:17:1097462. doi: 10.3389/fncel.2023.1097462. eCollection 2023.

Authors

Björn Trebels¹, Stefan Dippel¹, Janet Anders¹, Clara Ernst¹, Brigitte Goetz¹, Tim Keyser¹, Karl Heinz Rexer², Ernst A Wimmer³, Joachim Schachtner^{1

4}

Affiliations

¹ Animal Physiology, Department of Biology, Philipps-University Marburg, Marburg, Germany.
² Biodiversity of Plants, Department of Biology, Philipps-University Marburg, Marburg, Germany.
³ Department of Developmental Biology, Johann-Friedrich-Blumenbach-Institute for Zoology and Anthropology, Georg-August-University Göttingen, Göttingen, Germany.
⁴ Clausthal University of Technology, Clausthal-Zellerfeld, Germany.

Abstract

The paired antennal lobes were long considered the sole primary processing centers of the olfactory pathway in holometabolous insects receiving input from the olfactory sensory neurons of the antennae and mouthparts. In hemimetabolous insects, however, olfactory cues of the antennae and palps are processed separately. For the holometabolous red flour beetle Tribolium castaneum, we could show that primary processing of the palpal and antennal olfactory input also occurs separately and at distinct neuronal centers. While the antennal olfactory sensory neurons project into the antennal lobes, those of the palps project into the paired glomerular lobes and the unpaired gnathal olfactory center. Here we provide an extended analysis of the palpal olfactory pathway by combining scanning electron micrographs with confocal imaging of immunohistochemical staining and reporter expression identifying chemosensory and odorant receptor-expressing neurons in the palpal sensilla. In addition, we extended the anatomical characterization of the gnathal olfactory center by 3D reconstructions and investigated the distribution of several neuromediators. The similarities in the neuromediator repertoire between antennal lobes, glomerular lobes, and gnathal olfactory center underline the role of the latter two as additional primary olfactory processing centers.

Keywords: Tribolium castaneum; chemosensation; gnathal olfactory center; insect; lobus glomerulatus; neuroanatomy; olfaction; palpal sensilla.

Grants and funding

Parts of this study were funded within the Deutsche Forschungsgemeinschaft SPP 1392: SCHA 678/13-1 (JS) and WI 1797/4-1 (EW). The funders had no role in the study design, data collection, interpretation, or the decision to submit the work for publication.